Control of peak engine output in an engine with a knock suppression fluid

ABSTRACT

A method for supplying two types of fuel to an engine of a vehicle is disclosed. In one embodiment, an amount of a first fuel supplied to the engine is adjusted in response to a condition of a fuel separator. The method can improve vehicle drivability at least during some conditions.

BACKGROUND AND SUMMARY

Engines may use various forms of fuel delivery to provide a desiredamount of fuel for combustion in each cylinder. One type of fueldelivery uses a port injector for each cylinder to deliver fuel torespective cylinders. Still another type of fuel delivery uses a directinjector for each cylinder.

Further, engines have been proposed using more than one type of fuelinjection. For example, the papers titled “Calculations of KnockSuppression in Highly Turbocharged Gasoline/Ethanol Engines Using DirectEthanol Injection” and “Direct Injection Ethanol Boosted Gasoline EngineBiofuel Leveraging for Cost Effective Reduction of Oil Dependence andCO2 Emissions” by Heywood et al. are one example. Specifically, theHeywood et al. papers describe directly injecting ethanol to improvecharge cooling effects, while relying on port injected gasoline forproviding the majority of combusted fuel over a drive cycle. The ethanolprovides increased octane and increased charge cooling due to its higherheat of vaporization compared with gasoline, thereby reducing knocklimits on boosting and/or compression ratio. Further, water may be mixedwith ethanol and/or used as an alternative to ethanol. The aboveapproaches purport to improve engine fuel economy and increaseutilization of renewable fuels.

One issue recognized by the inventor herein with the above approach isthat the system may abruptly exhaust a supply of the ethanol, or otherknock suppression fuel, and thus abruptly lose the ability to operate athigh engine output torque with reduced knock. This can be especiallydramatic when the vehicle is operating at high output conditions, suchas trailer towing or under mountainous driving conditions. Thus, toavoid significant knocking upon such conditions, the engine mustabruptly retard spark and/or reduce boost, thus significantly reducingengine power or torque output.

One approach to address the above issues is to adjust maximum allowableengine power or torque output in response to availability of a knocksuppression mixture. For example, the peak torque output of the enginemay be gradually reduced (e.g., ramped, etc.) before the knocksuppression fluid is depleted so that when the fluid is depleted, theoperator does not experience a significant and/or rapid decrease in peakoutput. In this way, improved driver perception can be achieved.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a generic engine system;

FIG. 2 shows a partial engine view;

FIG. 3 shows an engine with a turbocharger;

FIG. 4 shows an example fuel system layout;

FIGS. 5-6 show example enablement routines;

FIGS. 7, 9, and 11 show alternative fuel system layouts;

FIGS. 8, 10, and 12 show separator control routines for various fuelsystem layouts;

FIGS. 13, 14, and 15 show graphs of example parameter variation;

FIG. 16 shows an example routine for controlling engine and separatoroperation; and

FIGS. 17-20 are graphs illustrating example operation with respect toFIG. 16.

DETAILED DESCRIPTION

FIG. 1 shows an engine 10 receiving delivery of a plurality ofsubstances (1, 2, . . . , N) via arrow 8. The various substances mayinclude multiple different fuel blends, injection locations, or variousother alternatives. In one example, multiple different substances havingdifferent gasoline and/or alcohol and/or water concentrations may bedelivered to the engine, and may be delivered in a mixed state, orseparately delivered. Further, the relative amounts and/or ratios of thedifferent substances may be variable controlled by a controller 6 inresponse to operating conditions, which may be provided via sensor(s) 4.

In one example, the different substances may represent different fuelshaving different levels of alcohol, including one substance beinggasoline and the other being ethanol. In another example, engine 10 mayuse gasoline as a first substance and an alcohol containing fuel such asethanol, methanol, a mixture of gasoline and ethanol (e.g., E85 which isapproximately 85% ethanol and 15% gasoline), a mixture of gasoline andmethanol (e.g., M85 which is approximately 85% methanol and 15%gasoline), a mixture of an alcohol and water, a mixture of an alcohol,water, and gasoline, etc as a second substance. In still anotherexample, the first substance may be a gasoline alcohol blend with alower alcohol concentration than a gasoline alcohol blend of a secondsubstance.

In another embodiment, different injector locations may be used fordifferent substances. For example, a single injector (such as a directinjector) may be used to inject a mixture of two substances (e.g.,gasoline and an alcohol/water mixture), where the relative amount orratio of the two substances in the mixture may be varied during engineoperation via adjustments made by controller 6 via a mixing valve (notshown), for example. In still another example, two different injectorsfor each cylinder are used, such as port and direct injectors, eachinjecting a different substance in different relative amounts asoperating conditions vary. In even another embodiment, different sizedinjectors, in addition to different locations and different substances,may be used. In yet another embodiment, two port injectors withdifferent spray patterns and/or aim points may be used.

As will be described in more detail below, various advantageous resultsmay be obtained by various of the above systems. For example, when usingboth gasoline and a fuel having alcohol (e.g., ethanol), it may bepossible to adjust the relative amounts of the fuels to take advantageof the increased charge cooling of alcohol fuels (e.g., via directinjection) to reduce the tendency of knock (e.g., in response to knockor increased load, increasing a relative amount of alcohol and/water).This phenomenon, combined with increased compression ratio, and/orboosting and/or engine downsizing, can then be used to obtain large fueleconomy benefits (by reducing the knock limitations on the engine),while allowing engine operation on gasoline at lighter loads when knockis not a constraint. However, when combusting a mixture having alcohol,the likelihood of pre-ignition may be increased under certain operatingconditions. As such, in one example, by utilizing water instead of ormixed into the substance having alcohol, it may be possible to reducethe likelihood of pre-ignition, while still taking advantage ofincreased charge cooling effects and the availability of alcoholcontaining fuels.

Referring now to FIG. 2, it shows one cylinder of a multi-cylinderengine, as well as the intake and exhaust path connected to thatcylinder. Further, FIG. 2 shows one example fuel system with two fuelinjectors per cylinder, for at least one cylinder. In one embodiment,each cylinder of the engine may have two fuel injectors. The twoinjectors may be configured in various locations, such as two portinjectors, one port injector and one direct injector (as shown in FIG.2), or others.

Also, as described herein, there are various configurations of thecylinders, fuel injectors, and exhaust system, as well as variousconfigurations for the fuel vapor purging system and exhaust gas oxygensensor locations.

Continuing with FIG. 2, it shows a multiple injection system, whereengine 10 has both direct and port fuel injection, as well as sparkignition. Internal combustion engine 10, comprising a plurality ofcombustion chambers, is controlled by electronic engine controller 12.Combustion chamber 30 of engine 10 is shown including combustion chamberwalls 32 with piston 36 positioned therein and connected to crankshaft40. A starter motor (not shown) may be coupled to crankshaft 40 via aflywheel (not shown), or alternatively direct engine starting may beused.

In one particular example, piston 36 may include a recess or bowl (notshown) to help in forming stratified charges of air and fuel, ifdesired. However, in an alternative embodiment, a flat piston may beused.

Combustion chamber, or cylinder, 30 is shown communicating with intakemanifold 44 and exhaust manifold 48 via respective intake valves 52 aand 52 b (not shown), and exhaust valves 54 a and 54 b (not shown).Thus, while four valves per cylinder may be used, in another example, asingle intake and single exhaust valve per cylinder may also be used. Instill another example, two intake valves and one exhaust valve percylinder may be used.

Combustion chamber 30 can have a compression ratio, which is the ratioof volumes when piston 36 is at bottom center to top center. In oneexample, the compression ratio may be approximately 9:1. However, insome examples where different fuels are used, the compression ratio maybe increased. For example, it may be between 10:1 and 11:1 or 11:1 and12:1, or greater.

Fuel injector 66A is shown directly coupled to combustion chamber 30 fordelivering injected fuel directly therein in proportion to the pulsewidth of signal dfpw received from controller 12 via electronic driver68A. While FIG. 2 shows injector 66A as a side injector, it may also belocated overhead of the piston, such as near the position of spark plug92. Such a position may improve mixing and combustion due to the lowervolatility of some alcohol based fuels. Alternatively, the injector maybe located overhead and near the intake valve to improve mixing.

Fuel and/or water may be delivered to fuel injector 66A by a highpressure fuel system (not shown) including a fuel tank, fuel pumps, anda fuel rail. Alternatively, fuel and/or water may be delivered by asingle stage fuel pump at lower pressure, in which case the timing ofthe direct fuel injection may be more limited during the compressionstroke than if a high pressure fuel system is used. Further, while notshown, the fuel tank (or tanks) may (each) have a pressure transducerproviding a signal to controller 12.

Fuel injector 66B is shown coupled to intake manifold 44, rather thandirectly to cylinder 30. Fuel injector 66B delivers injected fuel inproportion to the pulse width of signal pfpw received from controller 12via electronic driver 68B. Note that a single driver 68 may be used forboth fuel injection systems, or multiple drivers may be used. Fuelsystem 164 is also shown in schematic form delivering vapors to intakemanifold 44, where fuel system 164 is also coupled to injectors 66A and66B (although not shown in this Figure). Various fuel systems and fuelvapor purge systems may be used.

Intake manifold 44 is shown communicating with throttle body 58 viathrottle plate 62. In this particular example, throttle plate 62 iscoupled to electric motor 94 so that the position of elliptical throttleplate 62 is controlled by controller 12 via electric motor 94. Thisconfiguration may be referred to as electronic throttle control (ETC),which can also be utilized during idle speed control. In an alternativeembodiment (not shown), a bypass air passageway is arranged in parallelwith throttle plate 62 to control inducted airflow during idle speedcontrol via an idle control by-pass valve positioned within the airpassageway.

Exhaust gas sensor 76 is shown coupled to exhaust manifold 48 upstreamof catalytic converter 70 (where sensor 76 can correspond to variousdifferent sensors). For example, sensor 76 may be any of many knownsensors for providing an indication of exhaust gas air/fuel ratio suchas a linear oxygen sensor, a UEGO, a two-state oxygen sensor, an EGO, aHEGO, or an HC or CO sensor. In this particular example, sensor 76 is atwo-state oxygen sensor that provides signal EGO to controller 12 whichconverts signal EGO into two-state signal EGOS. A high voltage state ofsignal EGOS indicates exhaust gases are rich of stoichiometry and a lowvoltage state of signal EGOS indicates exhaust gases are lean ofstoichiometry. Signal EGOS may be used to advantage during feedbackair/fuel control to maintain average air/fuel at stoichiometry during astoichiometric homogeneous mode of operation. Further details ofair-fuel ratio control are included herein.

Distributorless ignition system 88 provides ignition spark to combustionchamber 30 via spark plug 92 in response to spark advance signal SA fromcontroller 12.

Controller 12 may cause combustion chamber 30 to operate in a variety ofcombustion modes, including a homogeneous air/fuel mode and/or astratified air/fuel mode by controlling injection timing, injectionamounts, spray patterns, etc. Further, combined stratified andhomogenous mixtures may be formed in the chamber. In one example,stratified layers may be formed by operating injector 66A during acompression stroke. In another example, a homogenous mixture may beformed by operating one or both of injectors 66A and 66B during anintake stroke (which may be open valve injection). In yet anotherexample, a homogenous mixture may be formed by operating one or both ofinjectors 66A and 66B before an intake stroke (which may be closed valveinjection). In still other examples, multiple injections from one orboth of injectors 66A and 66B may be used during one or more strokes(e.g., intake, compression, exhaust, etc.). Even further examples may bewhere different injection timings and mixture formations are used underdifferent conditions, as described below.

Controller 12 can control the amount of fuel delivered by fuel injectors66A and 66B so that the homogeneous, stratified, or combinedhomogenous/stratified air/fuel mixture in chamber 30 can be selected tobe at stoichiometry, a value rich of stoichiometry, or a value lean ofstoichiometry.

While FIG. 2 shows two injectors for the cylinder, one being a directinjector and the other being a port injector, in an alternativeembodiment two port injectors for the cylinder may be used, along withopen valve injection, for example.

Emission control device 72 is shown positioned downstream of catalyticconverter 70. Emission control device 72 may be a three-way catalyst ora NOx trap, or combinations thereof.

Controller 12 is shown as a microcomputer, including microprocessor unit102, input/output ports 104, an electronic storage medium for executableprograms and calibration values shown as read only memory chip 106 inthis particular example, random access memory 108, keep alive memory110, and a conventional data bus. Controller 12 is shown receivingvarious signals from sensors coupled to engine 10, in addition to thosesignals previously discussed, including measurement of inducted mass airflow (MAF) from mass air flow sensor 100 coupled to throttle body 58;engine coolant temperature (ECT) from temperature sensor 112 coupled tocooling sleeve 114; a profile ignition pickup signal (PIP) from Halleffect sensor 118 coupled to crankshaft 40; and throttle position TPfrom throttle position sensor 120; absolute Manifold Pressure Signal MAPfrom sensor 122; an indication of knock from knock sensor 182; and anindication of absolute or relative ambient humidity from sensor 180.Engine speed signal RPM is generated by controller 12 from signal PIP ina conventional manner and manifold pressure signal MAP from a manifoldpressure sensor provides an indication of vacuum, or pressure, in theintake manifold. During stoichiometric operation, this sensor can givean indication of engine load. Further, this sensor, along with enginespeed, can provide an estimate of charge (including air) inducted intothe cylinder. In one example, sensor 118, which is also used as anengine speed sensor, produces a predetermined number of equally spacedpulses every revolution of the crankshaft.

Continuing with FIG. 2, a variable camshaft timing system is shown.Specifically, camshaft 130 of engine 10 is shown communicating withrocker arms 132 and 134 for actuating intake valves 52 a, 52 b andexhaust valves 54 a, 54 b. Camshaft 130 is directly coupled to housing136. Housing 136 forms a toothed wheel having a plurality of teeth 138.Housing 136 is hydraulically coupled to crankshaft 40 via a timing chainor belt (not shown). Therefore, housing 136 and camshaft 130 rotate at aspeed substantially equivalent to the crankshaft. However, bymanipulation of the hydraulic coupling as will be described laterherein, the relative position of camshaft 130 to crankshaft 40 can bevaried by hydraulic pressures in advance chamber 142 and retard chamber144. By allowing high pressure hydraulic fluid to enter advance chamber142, the relative relationship between camshaft 130 and crankshaft 40 isadvanced. Thus, intake valves 52 a, 52 b and exhaust valves 54 a, 54 bopen and close at a time earlier than normal relative to crankshaft 40.Similarly, by allowing high pressure hydraulic fluid to enter retardchamber 144, the relative relationship between camshaft 130 andcrankshaft 40 is retarded. Thus, intake valves 52 a, 52 b, and exhaustvalves 54 a, 54 b open and close at a time later than normal relative tocrankshaft 40.

While this example shows a system in which the intake and exhaust valvetiming are controlled concurrently, variable intake cam timing, variableexhaust cam timing, dual independent variable cam timing, or fixed camtiming may be used. Further, variable valve lift may also be used.Further, camshaft profile switching may be used to provide different camprofiles under different operating conditions. Further still, thevalvetrain may be roller finger follower, direct acting mechanicalbucket, electromechanical, electrohydraulic, or other alternatives torocker arms.

Continuing with the variable cam timing system, teeth 138, being coupledto housing 136 and camshaft 130, allow for measurement of relative camposition via cam timing sensor 150 providing signal VCT to controller12. Teeth 1, 2, 3, and 4 are preferably used for measurement of camtiming and are equally spaced (for example, in a V-8 dual bank engine,spaced 90 degrees apart from one another) while tooth 5 is preferablyused for cylinder identification, as described later herein. Inaddition, controller 12 sends control signals (LACT, RACT) toconventional solenoid valves (not shown) to control the flow ofhydraulic fluid either into advance chamber 142, retard chamber 144, orneither.

Relative cam timing can be measured in a variety of ways. In generalterms, the time, or rotation angle, between the rising edge of the PIPsignal and receiving a signal from one of the plurality of teeth 138 onhousing 136 gives a measure of the relative cam timing. For theparticular example of a V-8 engine, with two cylinder banks and afive-toothed wheel, a measure of cam timing for a particular bank isreceived four times per revolution, with the extra signal used forcylinder identification.

Sensor 160 may also provide an indication of oxygen concentration in theexhaust gas via signal 162, which provides controller 12 a voltageindicative of the O2 concentration. For example, sensor 160 can be aHEGO, UEGO, EGO, or other type of exhaust gas sensor. Also note that, asdescribed above with regard to sensor 76, sensor 160 can correspond tovarious different sensors.

As described above, FIG. 2 merely shows one cylinder of a multi-cylinderengine, and it is understood that each cylinder has its own set ofintake/exhaust valves, fuel injectors, spark plugs, etc.

Also, in the example embodiments described herein, the engine may becoupled to a starter motor (not shown) for starting the engine. Thestarter motor may be powered when the driver turns a key in the ignitionswitch on the steering column, for example. The starter is disengagedafter engine starting, for example, by engine 10 reaching apredetermined speed after a predetermined time. Further, in thedisclosed embodiments, an exhaust gas recirculation (EGR) system may beused to route a desired portion of exhaust gas from exhaust manifold 48to intake manifold 44 via an EGR valve (not shown). Alternatively, aportion of combustion gases may be retained in the combustion chambersby controlling valve timing.

As noted above, engine 10 may operate in various modes, including leanoperation, rich operation, and “near stoichiometric” operation. “Nearstoichiometric” operation can refer to oscillatory operation around thestoichiometric air fuel ratio. Typically, this oscillatory operation isgoverned by feedback from exhaust gas oxygen sensors. In this nearstoichiometric operating mode, the engine may be operated withinapproximately one air-fuel ratio of the stoichiometric air-fuel ratio.

Feedback air-fuel ratio control may be used for providing the nearstoichiometric operation. Further, feedback from exhaust gas oxygensensors can be used for controlling air-fuel ratio during lean andduring rich operation. In particular, a switching type, heated exhaustgas oxygen sensor (HEGO) can be used for stoichiometric air-fuel ratiocontrol by controlling fuel injected (or additional air via throttle orVCT) based on feedback from the HEGO sensor and the desired air-fuelratio. Further, a UEGO sensor (which provides a substantially linearoutput versus exhaust air-fuel ratio) can be used for controllingair-fuel ratio during lean, rich, and stoichiometric operation. In thiscase, fuel injection (or additional air via throttle or VCT) can beadjusted based on a desired air-fuel ratio and the air-fuel ratio fromthe sensor. Further still, individual cylinder air-fuel ratio controlcould be used, if desired. Adjustments may be made with injector 66A,66B, or combinations thereof depending on various factors, to controlengine air-fuel ratio.

Also note that various methods can be used to maintain the desiredtorque such as, for example, adjusting ignition timing, throttleposition, variable cam timing position, exhaust gas recirculationamount, and number of cylinders carrying out combustion. Further, thesevariables can be individually adjusted for each cylinder to maintaincylinder balance among all the cylinders. While not shown in FIG. 2,engine 10 may be coupled to various boosting devices, such as asupercharger or turbocharger, as shown in FIG. 3. On a boosted engine,desired torque may also be maintained by adjusting wastegate and/orcompressor bypass valves.

Referring now specifically to FIG. 3, an example engine 10 is shown withfour in-line cylinders. In one embodiment, engine 10 may have aturbocharger 319, which has a turbine 319 a coupled to the exhaustmanifold 48 and a compressor 319 b coupled to the intake manifold 44.While FIG. 3 does not show an intercooler, one may optionally be used.Turbine 319 a is typically coupled to compressor 319 b via a drive shaft315. Various types of turbochargers and arrangements may be used. Forexample, a variable geometry turbocharger (VGT) may be used where thegeometry of the turbine and/or compressor may be varied during engineoperation by controller 12. Alternately, or in addition, a variablenozzle turbocharger (VNT) may be used when a variable area nozzle isplaced upstream and/or downstream of the turbine in the exhaust line(and/or upstream or downstream of the compressor in the intake line) forvarying the effective expansion or compression of gasses through theturbocharger. Still other approaches may be used for varying expansionin the exhaust, such as a waste gate valve. FIG. 3 shows an examplebypass valve 320 around turbine 319 a and an example bypass valve 322around compressor 319 b, where each valve may be controlled viacontroller 12. As noted above, the valves may be located within theturbine or compressor, or may be a variable nozzle.

Also, a twin turbocharger arrangement, and/or a sequential turbochargerarrangement, may be used if desired. In the case of multiple adjustableturbocharger and/or stages, it may be desirable to vary a relativeamount of expansion though the turbocharger, depending on operatingconditions (e.g. manifold pressure, airflow, engine speed, etc.).Further, a mechanically or electrically driven supercharger may be used,if desired.

Referring now to FIG. 4, an example fuel system layout is provided withfuel tank 410 having fuel fill cap 412. The system is configured toreceive a fuel mixture through the fill line 414 and into tank 410,where the mixture may be a gasoline/alcohol mixture, agasoline/alcohol/water mixture, or various others such as noted herein,including, a gasoline/ethanol mixture such as E10, for example. The fuelmixture in tank 410 may be transported to a separate system 420 via atransport system, shown by double arrow 416. The transport system 416may be a one way transport, e.g., transporting the fuel mixture to theseparator, or may enable two-way transportation, such as return linesfrom the separator or downstream fuel system back to the tank 410. Thetransport system 416 may include pumps, valves, multiple separate lines,or various other components, such as described below herein with regardto example systems. Further, while FIG. 4 shows the transport system 416external to tank 410, system 416 along with separate 420 and/or portionsof transport system 422 may also be located within or at least partiallywithin tank 410.

Separator 420 may include various types of separator system. Theseparator system is generally configured to allow two or more componentsin the fuel mixture stored in tank 410 to be separated and providedseparately to engine 10, thereby permitting the advantages of multipleor mixed injection strategies to be employed without causinginconvenience to a user. In one example, the separator system utilizesan aqueous extraction to remove fuel components soluble in water (suchas methanol, ethanol, etc.) from fuel components not soluble in water.For example, an extraction fluid (e.g., water) may be added to agasoline/alcohol mixture, and the mixture drawn off at different levels,where the lower level provides an alcohol enriched substance. In anotherexample, a barrier in a tank may be used, where the barrier is made atleast partially of a material or materials that selectively transportsone component of the mixed fuel at a higher rate than, or even to thesubstantial exclusion of, the other component of the mixed fuel. Instill another example, the barrier may be an ionically or electricallyconductive polymeric or inorganic material, polypyrole being one exampleof a conductive polymer. A voltage and/or current may be applied acrossand/or through the membrane using a voltage and/or current supply,respectively. In this way, substances may be extracted at differentrates and/or concentrations, for example.

Continuing with FIG. 4, it also shows downstream transport system 422located between separator 420 and the engine (not shown). Transportsystem 422 is shown having at least two separate lines coupled to theseparator to transport different amounts of substances with differentconstituents to the engine depending on operating conditions. Transportsystem 422 may maintain the different substances separate in deliveringthe substances to the engine, or may mix the substances for co-deliveryto the engine, as illustrated in FIG. 4. Further, like system 416,system 422 may include pumps, valves, multiple separate lines, returnlines, or various other components, such as described below herein withregard to example systems

Referring now to FIGS. 5-6, example routines for controlling systemoperations are provided, in particular for enabling and controllingseparator operation. In 510, the routine reads operating conditions,such as those noted below in FIG. 6. Then, in 512, the routinedetermines whether conditions for enabling separator operation are met.Various conditions may be used to enable/disable separate operation,such as those noted with regard to FIG. 6. If the answer to 512 is no,the routine continues to 514 to disable separator operation and then toshowdown the separator in 516 if it is not already deactivated. Theshutdown may be a gradual shutdown, or may be adjusted depending on theoperating conditions. For example, under some conditions, a more rapidshutdown may be used than other conditions.

If the answer to 512 is yes, the routine continues to 518 to enableseparator operation. Then in 520, the routine performs an activationsequence to activate the separator if it is not already active. Theactivation sequence may include warm-up operation to initiateseparation, and may be adjusted depending on engine, vehicle, and/orambient operating conditions. For example, the separator may have a morerapid activation sequence under warmer ambient conditions.

Referring now to FIG. 6, details of the separator enablement aredescribed. While the following conditions may be used to enable/disableseparator operation, various other or alternative combinations of theseparameters may be used. In 610, the routine first determines whetherseparator degradation has occurred or been detected. Degradation may bedetected in a variety of ways, such as based on measured separatoroperation compared to expected operation for a given set of conditions.For example, the routine may monitor separator performance, fuelseparation rate, fuel separation percentage yield, or various others. Ifthe answer to 610 is no, the routine continues to 612 to determinewhether fuel temperature is outside a range for separator operation. Therange may vary with operating conditions such as an estimate of fueltypes in the tank or separator, relative fuel quantities, in the tank orseparator, or various others.

If the answer to 612 is no, the routine continues to 614 to determinewhether the separator and/or any of its components are outside atemperature range for separator operation. Again, the range may varywith operating conditions such as an estimate of fuel types in the tankor separator, relative fuel quantities in the tank or separator, engineoperating conditions, or various others.

If the answer to 614 is no, the routine continues to 616 to determinehow in the case of an electrically actuated separator, electrical powerrelated values compare to acceptable values or thresholds. For example,the routine may determine whether the amount of energy used by theseparator in separating the current fuel under the current conditions isless than a threshold value. Alternatively, the routine may considervehicle battery voltage, state of charge, and/or electrical powergeneration conditions. For example, if battery voltage or state ofcharge is above a threshold valve, separator operation may be enabled.

If the answer to 616 is no, the routine continues to 618 to determinewhether tank fuel mixture constituents are outside selected ranges inwhich separator operation is performed. For example, if a certainconstituent to be separated is below a certain relative amount in theincoming fuel, separation may be disabled due to low yields.Alternatively, if another constituent is above a threshold valve,separation may be disabled due to interference in separationperformance.

If the answer to 618 is no, the routine continues to 620 to determinewhether, in the case of alcohol separation, an alcohol concentration inthe fuel tank mixture is less than a threshold value. For example, ifthe amount of alcohol in the mixture is below a threshold, separationmay be disabled due to low alcohol availability.

If the answer to 620 is no, the routine continues to 622 to determinewhether, in the case of alcohol separation, alcohol requirements areless than a threshold value. For example, if the engine and/or vehicleare operating under conditions in which a separated alcohol mixture isnot needed, or only minimally needed, separation may be disabled. In oneexample, if the engine coolant temperature is less than a minimumtemperature (e.g., during a cold start), the separated mixture may notbe used, and thus the separator may be disabled. Likewise, if theseparated mixture is delivered via a separate injection system that hasdegraded, separator operation may be disabled.

From a yes answer to any of 610 through 622, the routine continues to626 to disable separation. Alternatively, if the answer to 622 is no,the routine continues to 624 to enable separator operation. In this way,it is possible to provide appropriate operation of the separator in thecontext of vehicle operation and degradation over vehicle life.

Referring now to FIGS. 7, 9, and 11, example fuel systems areillustrated, along with associated control routines for separator and/orengine control.

Specifically, FIG. 7 illustrates an example fuel system layout in whicha separator 720 is used to separate at least ethanol from a fuel mixturein tank 710 having at least gasoline and ethanol. In one example, theseparator may receive as an input a gasoline/ethanol mixture 716 with afirst ethanol concentration and generate two output gasoline/ethanolmixtures (730, 732), one with a second ethanol concentration and onewith a third ethanol concentration. In one example, the third ethanolconcentration is higher than the first ethanol concentration, which ishigher than the second ethanol concentration. The two outputs mixturesare fed to engine 10, for example, output 730 may be fed to a port fuelinjector (e.g., 66A) and output 732 may be fed to a direct injector(e.g., 66B).

In one example, a pump 750 may be provided to pressurize the mixture716, shown in dashed lines. In addition, or alternatively, pumps 752 and754 may be provided in 730 and 732, respectively. The pump(s) may becontrolled via controller 12, which also receives various inputs, suchas information from sensor(s) 742. Further, controller 12 may controlseparator 720, in addition to engine and/or vehicle operation.

For the example system of FIG. 7, it may advantageously be used in thecase that the separate can generate sufficient quantities of a higheralcohol concentration fuel mixture to handle a substantial portion ofengine and/or vehicle operation, and as such an additional storage tankfor one or both of mixtures 730 and 732 is not required (although it maybe added, if desired).

In this case, one optional control strategy for the separator mayinclude operating the separator at various production/generation ratesand/or concentrations depending on engine fueling requirements andoperating conditions. In one embodiment, the controller may operate theseparator in a manner sufficient to produce a required alcohol amountfor the current engine operating conditions or current engine fuelingdemand. The current engine demand could be determined from the enginecontroller, or calculated from injector pulsewidth and fuel pressure.Alternatively, feedback control of fuel pressure or another parametercould be used to supply enough production to meet demand and maintainpressure.

For example, in the case where the mixture in 732 has a higher alcoholconcentration than that of 730, the separator may be controlled inresponse to which mixture is limiting. In other words, in the case wheremixture 732 is being used faster than generation/separation, theseparator may be adjusted to increase the amount of mixture 732.Likewise, in the case where mixture 730 is being used faster thangeneration/separation, the separator may be adjusted to increase theamount of mixture 730. In these cases, return lines (not shown) may beused to return excess amounts of mixtures 730 and/or 732 to tank 710.

If the separator transient response is slower than required for theengine, feed forward controls can be used, where a predicted demand iscalculated based on current and/or past operating conditions, as well asadaptive learning, for example. In another example, this may involvepredictions of future engine demand based on recent demand, earlierpatterns of demand, fuzzy logic, etc. Alternatively, the separator couldalways operate at a higher rate than currently necessary (with unusedethanol returned to the tank via optional return line 734). The amountof excess separation could also be varied based on operating conditionssuch as recent demand, earlier patterns of demand, fuzzy logic, etc. Instill another alternative, the amount of excess separation/generationcould be a function of current demand for mixture 732, enginespeed/load/temperature, and/or combinations thereof.

The level of detail in control adjustments and/or accuracy desired maydepend on parasitic losses of the ethanol separator. For example, in thecase of an electrically actuated/powered separator, if the separatorelectric power or other input requirements are relatively low (e.g. lessthan a threshold value), the separator may operate whenever the engineis running, or with simple on/off control whenever some ethanol isdemanded. However, if parasitic losses are greater, two or three levelmodulation of the separator may be used. Further, if parasitic lossesare still greater, then the more detailed enablement of FIG. 6 may beused, along with the varying operation of FIG. 8 may be used to reducethe losses by operating with reduced excess separation and with thelevel of separation matched to current and/or future predicted operatingconditions.

Specifically, with regard to FIG. 8, a routine is described forcontrolling separator operation, such as for the configuration of FIG.7. In 810, the routine determines a desired generation rate of a firstand second mixture from the separator based on operating conditions,such as engine demand, fueling demand, driver input, and/or combinationsthereof as noted above herein. Further, in addition to a desiredgeneration rate, the routine may also determine a desired concentrationof the output mixtures. In addition, the routine may determine whichdesired rate is limiting the generation rates of multiple outputmixtures which are interdependent. Then, in 812, the routine adjusts theseparator to provide at least one of the desired generation rates (orconcentrations) of the limiting mixture.

Referring now to FIG. 9, another example fuel system is provided similarto that of FIG. 7, except that each of two output mixtures 930 and 932having respective storage tanks 960 and 962 to enable buffering of thegeneration rate from the engine usage rate. In this way, it is possibleto provide more consistent generation rate and thereby improvegeneration efficiency under selected conditions. Specifically, in FIG.9, two storage tanks 960 and 962 (each having an optional pump 952 and954 therein, respectively) receive outputs from separator 720 via lines930 and 932, respectively, and provide mixtures 934 and 936 to engine10. As noted above, the mixture of 934 may be fed to a port injector ofa cylinder, and the mixture of 936 may be fed to a direct injector in acylinder in engine 10.

Due to the ability to store both of the generated mixtures, with thisfuel system it may be possible to control separator 720 to provideimproved generation efficiency, while also providing sufficientgeneration to maintain sufficient fuel mixtures in both tanks 960 and962.

Referring now to FIG. 10, a routine is described for controlling atleast separator operation. Specifically, in 1010, the routine determinesdemand levels for the substances of tanks 960 and 962, respectively. Asnoted herein, the demand may be based on current or predicted enginefueling requirements, torque requests, or various others.

Next, in 1012, the routine determines the desired fill levels of tanks960 and 962, respectively, which may be based on current engine,vehicle, and/or ambient operating conditions. Then, in 1014, the routineadjusts separator operation (e.g., separator rate, efficiency, or other)based on the desired fill levels and demand levels. For example, it maybe desirable to provide sufficient fuel in tank 960 (which may begasoline with a lower alcohol concentration than provided or in tank962), which may be preferable to improve fuel vaporization and transientA/F control under selected conditions, and therefore reduce exhaustemissions for a cold start. For example, in this case, the separatorcontrols may continue operating the separator when tank 962 issufficiently filled, so that sufficient fuel is stored in tank 960 forthe next cold start.

As another example, the separator may shift production between thehigher and lower alcohol concentration outputs so as to not overfilleither of tanks 960 or 962. Or the separator may be operated to ensuresufficient alcohol-rich mixture in tank 962 for one or more wide-openthrottle accelerations to highway speed.

Referring now to FIG. 11, another example fuel system is providedsimilar to that of FIGS. 7 and 9, except that only one of two outputmixtures (932) has a storage tank 962 to enable buffering of thegeneration rate from the engine usage rate. In this way, it is possibleto provide more consistent generation rate of the mixture in 932 andthereby improve generation efficiency under selected conditions, whilereducing system storage costs, since the excess generation from theother output mixture 930 is returned to tank 710 via line 934, e.g.,using pressure regulator 1170.

In one example, such a system can reduce the system size and cost andpackaging space by avoiding the separate tanks used in FIG. 9.

One example control routine for the configuration of FIG. 11 isillustrated in FIG. 12. In one embodiment, the control routines maymaintain sufficient mixture level in tank 962 with the higher alcoholconcentration (e.g., ethanol) to power the engine for one or morewide-open throttle accelerations to highway speed. Again, differentcontrol actions may be taken to account for variation of the size andthe parasitic losses of the separator. For example, if the separatorrequires low electric power or other inputs, it may operate whenevertank 962 is less than full (and optionally with some hysteresis).

Alternatively, if parasitic losses are higher, and/or if separatorefficiency is a function of separation rate, then additional controlactions may be taken. For example, more sophisticated controls describedbelow may be used to minimize the losses. Regardless of efficiency, theseparator may be operated at maximum or increased separation ratewhenever tank 962 is below a threshold value, which may be near empty.If parasitic losses are proportional to separation rate, then theseparator may be controlled to make separation rate substantiallyinversely proportional to tank level, as shown in FIG. 13. If separatorefficiency is maximum at some intermediate separation rate as shown inFIG. 14, the controls may maximize or increase time spent at or nearthat rate, as shown in FIG. 15. Further, combinations of the abovecontrols may be used. Further still, the above control adjustments toseparation rate may be translated into a feedback control routine forcontrolling fill level of one or more tanks by adjusting the separatorand/or other operating parameters.

Returning to FIG. 12, in 1210 the routine determines or measures acurrent tank fill level of tank 962. Next, in 1212, the routinedetermines a demand rate of fuel from tank 962 based on operatingconditions, including current and/or predicted conditions, for example.Then, in 1214, the routine adjusts separator operation based on adifference between a desired fill state (e.g., full, or partly filled)and the measured fill level, as well as based on the demand rate. Inthis way, it is possible to take into account both engine demand andtank fill conditions to provide sufficient and more efficientseparation.

Referring now specifically to FIG. 16, a routine is described foradjusting engine output limits, and thus usage rate of a knocksuppression fluid, based on an amount of storage of the knocksuppression fluid, such as a level in tank 962, for example.Specifically, the routine adjusts operation to reduce sudden decreasesin peak engine output caused by sudden unavailability of the knocksuppression fluid (e.g., due to depletion).

In other words, as shown by the graph of FIG. 17, in the case ofcontinuous high engine power demand, if a secondary fluid, such as aknock suppression fluid, is used indiscriminately, abrupt decreases inengine power may occur. For example, before time t1, sufficient knocksuppression fluid is available and being used to enable operation at ahigh engine power. However, at time t1, the storage is depleted and theusage rate is limited by the separator rate (here it is assumed that therate decreases due to a decrease in separator performance as the knocksuppression substance in the tank is depleted). Then, at time t3, thereis no substance to be separated left in the tank (e.g., 410, 710).

Likewise, in another example of intermittent high engine output demand,again the driver may experience an abrupt decrease in available engineoutput as illustrated in FIG. 18. This graph illustrates that at timet6, the knock suppression fuel is depleted, and thus at t7, the driversuddenly discovers a power loss. Specifically, before t6, the solid lineindicating driver request and the dashed line indicated output deliveredby the engine are aligned, whereas at t7, there may be a substantialdifference.

In another embodiment, the routine adjusts engine operation (e.g.,delivery of gasoline and a knock suppression fluid such as separatedethanol), based on the level of storage. Specifically, in 1610, theroutine determines an excess amount of knock suppression fluid, such asan amount stored in a tank greater than a minimum level. Next, in 1612,the routine determines whether the excess is less than a threshold valuein 1612. If not, the routine ends. Otherwise, the routine continues to1614 to determine a maximum engine torque reduction for the currentconditions, where the reduction may be a function of the excess. Forexample, the reduction may be proportional to the excess, where with alarger excess, the reduction is smaller and with a smaller excess, thereduction is greater. Further, the current conditions considered mayinclude engine speed (RPM), gear ratio of a transmission, and others.Next, in 1616, the routine limits engine torque via the reduction of1614, and then in 1618 the routine adjusts injection amount(s), throttleangle, boost amount, spark timing, exhaust gas recirculation amount, camtiming and/or valve timing, and others based on the limited torque valueof 1616.

In this way, a gradual reduction in engine output and vehicleperformance can be provided, thus reducing abrupt changes that may bemore objectionable to a vehicle operator. For example, as shown in FIG.19 (which shows an example similar to that of FIG. 17), full output maybe provided up to time t3, and then it may be more gradually reduced totime t4 before emptying storage of a knock suppression fluid, where timet4 is generally longer than t1 of FIG. 17. Again, after t4, theseparator capability dictates usage rates until t5 when there is nosubstance to be separated left in the tank. Likewise, FIG. 20 shows agraph similar to FIG. 18, but using a control routine to provide gradualpower decrease over a plurality of intermittent high power outputrequests. Specifically, between each of t8 and t9, and t10 and t11, agradual decrease is provided. Further, the dash dot lines illustratesthat the driver is able to return to a peak torque or power near thatpreviously provided.

It will be appreciated that the configurations, systems, and routinesdisclosed herein are exemplary in nature, and that these specificembodiments are not to be considered in a limiting sense, becausenumerous variations are possible. For example, the above approaches canbe applied to V-6, I-3, I-4, I-5, I-6, V-8, V-10, V-12, opposed 4, andother engine types.

As another example, engine 10 may be a variable displacement engine inwhich some cylinders (e.g., half) are deactivated by deactivating intakeand exhaust valves for those cylinders. In this way, improved fueleconomy may be achieved. However, as noted herein, in one exampleinjection using multiple types of fuel delivery (e.g., fuel compositionor delivery location) can be used to reduce a tendency of knock athigher loads. Thus, by operating for example with direct injection ofwater and/or a fuel containing alcohol (such as ethanol or an ethanolblend) during cylinder deactivation operation, it may be possible toextend a range of cylinder deactivation, thereby further improving fueleconomy.

As will be appreciated by one of ordinary skill in the art, the specificroutines described herein in the flowcharts and the specification mayrepresent one or more of any number of processing strategies such asevent-driven, interrupt-driven, multi-tasking, multi-threading, and thelike. As such, various steps or functions illustrated may be performedin the sequence illustrated, in parallel, or in some cases omitted.Likewise, the order of processing is not necessarily required to achievethe features and advantages of the example embodiments of the inventiondescribed herein, but is provided for ease of illustration anddescription. Although not explicitly illustrated, one of ordinary skillin the art will recognize that one or more of the illustrated steps orfunctions may be repeatedly performed depending on the particularstrategy being used. Further, these figures graphically represent codeto be programmed into the computer readable storage medium in controller12. Further still, while the various routines may show a “start” and“end” block, the routines may be repeatedly performed in an iterativemanner, for example.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “an” element or “a first” element or the equivalent thereof. Suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Other combinations and subcombinations of the disclosed features,functions, elements, and/or properties may be claimed through amendmentof the present claims or through presentation of new claims in this or arelated application. Such claims, whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

1. A method for a vehicle traveling on a road, comprising: receiving afuel mixture, said fuel mixture having at least some alcohol; separatingsaid fuel mixture into at least a first and second mixture on board thevehicle, where said first mixture has a higher alcohol concentrationthan said second mixture; delivering a first amount of said firstmixture and a second amount of said second mixture to an engine indifferent ratios as an operating condition varies; and adjusting anengine operating parameter to limit engine output torque or power basedon a separation rate of said first mixture from said fuel mixture. 2.The method of claim 1 wherein said adjusting said engine operatingparameter further comprises limiting maximum engine output based on anamount of said first mixture available.
 3. The method of claim 1 whereinsaid adjusting said engine operating parameter further comprisesgradually reducing a maximum limit of engine output before said firstmixture is depleted.
 4. The method of claim 1 wherein said adjustingsaid engine operating parameter further comprises gradually reducing amaximum limit of engine output over a duration after which said firstmixture is depleted.
 5. A method for a vehicle traveling on a road,comprising: receiving a fuel mixture, said fuel mixture having at leastsome alcohol; separating said fuel mixture into at least a first andsecond mixture on board the vehicle, where said first mixture has ahigher alcohol concentration than said second mixture; and delivering afirst amount of said first mixture and a second amount of said secondmixture to an engine in different ratios as an operating conditionvaries, where at least one of said first and second amounts is variedwith at least an operating parameter of the separation, wherein said atleast an operating parameter of the separation is a separation rate. 6.The method of claim 5 wherein said first mixture is directly injectedinto said engine.
 7. The method of claim 5 wherein said at least anoperating parameter of the separation includes a temperature of aseparator performing the separation.
 8. The method of claim 5 whereinsaid alcohol comprises ethanol.
 9. The method of claim 8 furthercomprising adjusting said separation based on an engine operatingcondition.
 10. The method of claim 9 wherein said engine operatingcondition includes engine load and engine temperature.
 11. The method ofclaim 8 wherein said fuel mixture further comprises water.
 12. Themethod of claim 5 further comprising adjusting an operating parameter ofthe engine based on said separation.
 13. A method for a vehicletraveling on a road, comprising: receiving a fuel mixture, said mixturehaving at least some alcohol; separating said fuel mixture into at leasta first and second mixture on board the vehicle, where said firstmixture has a higher alcohol concentration than said second mixture;delivering a first amount of said first mixture via a direct cylinderinjector and a second amount of said second mixture via a port injectorto an engine in different ratios as an operating condition varies; andlimiting engine output torque or power based on a separation rate ofsaid first mixture from said fuel mixture.
 14. The method of claim 13wherein said engine output is limited by adjusting boost amount.
 15. Asystem for a vehicle traveling on a road, the system comprising: adelivery system configured to deliver a first amount of a first mixtureand a second amount of a second mixture to an engine in differentratios, where said first mixture has a higher alcohol content than saidsecond mixture; and a control system configured to deliver a firstamount of said first mixture and a second amount of said second mixtureto the engine in different ratios as an operating condition varies, andto vary a concentration of alcohol in said first mixture, wherein saidcontrol system further gradually reduces maximum engine output as aproduction amount of said first mixture is reduced.
 16. The system ofclaim 15 wherein said control system further gradually reduces maximumengine output as a storage amount of said first mixture is reduced. 17.The system of claim 15 wherein said maximum engine output is reduced byadjusting at least one of a fuel injection amount, throttle angle, boostamount, spark timing, exhaust gas recirculation amount, cam timing, andvalve timing.
 18. The system of claim 15 wherein one of said first andsecond mixtures comprises at least some water.